1. Field of the Invention
The present invention relates to titanium oxide and barium titanate powders, methods of manufacturing the same, dielectric ceramics and multilayer ceramic capacitors, and particularly to an improved method for preparing a highly crystalline fine barium titanate powder.
2. Description of the Related Art
Sintering a powder material mainly containing barium titanate results in a dielectric ceramic. The dielectric ceramic is used, for example, for forming dielectric ceramic layers included in multilayer ceramic capacitors.
For miniaturizing the multilayer ceramic capacitors and giving them high capacitance, it is effective to form thinner dielectric ceramic layers. In order to form thin dielectric ceramic layers, the barium titanate powder used for the dielectric ceramic layers needs to be finer.
Hydrothermal synthesis and hydrolysis have been suggested and put to practical use to readily obtain fine barium titanate powders, but these methods increase the cost of manufacturing the barium titanate powders. Accordingly, solid-phase reaction has been traditionally used for manufacturing barium titanate powders.
In the solid-phase reaction, starting materials, for example, a barium carbonate powder and a titanium oxide powder are mixed, pulverized with a medium, and then are calcined. For manufacturing finer barium titanate powder by solid-phase reaction, it is effective to pulverize titanium oxide powder or to use a much finer titanium oxide powder.
Unfortunately, while barium titanate is synthesized at temperatures of 1000 to 1200° C., titanium oxide is sintered at about 800° C. Hence, titanium oxide starts to be sintered, that is, grains grow, before the barium titanate starts to be synthesized. As a result, even when the fine titanium oxide powder is used, it cannot be effective enough to obtain a fine barium titanate powder.